Update description

README.md

@@ -1,10 +1,14 @@
 # Direct-Van-der-Waals-Simulation-Code-Mesh
 Source code, mesh file and related software for Direct Van der Waals Simulation (DVS)
 
-# Content
+# Content Description
 - Software
-- Code2D
-- Code3D
-- Mesh
-- CaseFiles
-- PostProcess.py
+    - PETSC: Open source software for HPC.
+    - PetIGA: An isogeometric analysis software. 
+    - IGAKIT: Post process software for PetIGA. 
+    * The source code of PETSC, PetIGA and IGAKIT are all modified for this particular project
+- Code2D: DVS code for 2D simulations
+- Code3D: DVS code for 3D simulations
+- Mesh: Geometry used for DVS simulations
+- CaseFiles: Input files used for DVS simulations
+- PostProcess.py: Post process script